Electronic apparatus and flexible printed wiring board

Abstract

According to one embodiment, an electronic apparatus includes a flexible printed wiring board. The printed wiring board includes a conductive layer including a signal line and a ground line, a second insulating layer layered on the conductive layer and including openings open to above the ground line, a ground layer covering the signal line and electrically connected to the ground line, and a third insulating layer covering the ground layer. The ground layer includes first and second conductive pastes. The first conductive paste is filled in the openings so as to cover the ground line exposed to bottoms of the openings. The second conductive paste is applied so as to continuously cover the first conductive paste and the second insulating layer. The second conductive paste has a smaller volume resistivity than the first conductive paste.

1 . An electronic apparatus comprising a housing and a flexible printed wiring board provided in the housing, the flexible printed wiring board comprising:
 a first insulating layer;   a conductive layer layered on the first insulating layer, and comprising a signal line and a ground line;   a second insulating layer layered on the conductive layer, and comprising a plurality of openings open to above the ground line;   a ground layer layered on the second insulating layer so as to cover the signal line, and electrically connected to the ground line; and   a third insulating layer covering the ground layer, wherein   the ground layer comprises a first conductive paste filled in the plurality of openings so as to cover the ground line exposed to bottoms of the plurality of openings, and a second conductive paste applied so as to continuously cover the first conductive paste and the second insulating layer, the second conductive paste having a smaller volume resistivity than the first conductive paste.   
     
     
         2 . The electronic apparatus of  claim 1 , wherein the second conductive paste has a greater thixotropic ratio than the first conductive paste. 
     
     
         3 . The electronic apparatus of  claim 2 , wherein the signal line comprises a pair of differential transfer lines that transfer data at a rate according to a serial ATA standard. 
     
     
         4 . The electronic apparatus of  claim 3 , wherein the first and second conductive pastes each contain conductive particles and binder resin that binds the conductive particles, and the second conductive paste is filled at a greater fill volume than the first conductive paste. 
     
     
         5 . The electronic apparatus of  claim 4 , wherein the conductive particles of the second conductive paste have a larger shape than the conductive particles of the first conductive paste. 
     
     
         6 . The electronic apparatus of  claim 4 , wherein the first and second conductive pastes are applied onto the second insulating layer by a screen printing method. 
     
     
         7 . A flexible printed wiring board comprising:
 a first insulating layer;   a conductive layer layered on the first insulating layer, and comprising a signal line and a ground line;   a second insulating layer layered on the conductive layer, and comprising a plurality of openings open to above the ground line;   a ground layer layered on the second insulating layer so as to cover the signal line, and electrically connected to the ground line; and   a third insulating layer covering the ground layer, wherein   the ground layer comprises a first conductive paste filled in the plurality of openings so as to cover the ground line exposed to bottoms of the plurality of openings, and a second conductive paste applied so as to continuously cover the first conductive paste and the second insulating layer, the second conductive paste having a smaller volume resistivity than the first conductive paste.   
     
     
         8 . The flexible printed wiring board of  claim 7 , wherein the signal line comprises a pair of differential transfer lines that transfer data at a rate according to a serial ATA standard. 
     
     
         9 . The flexible printed wiring board of  claim 8 , wherein the plurality of openings are arranged at an interval maintained between each other, on the ground line. 
     
     
         10 . The flexible printed wiring board of  claim 9 , wherein the first conductive paste has flange parts which overhang the second insulating layer and are covered with the second conductive paste. 
     
     
         11 . A flexible printed wiring board comprising:
 a first insulating layer;   a conductive layer layered on the first insulating layer, and comprising a signal line and a ground line;   a second insulating layer layered on the conductive layer, and comprising a plurality of openings open to above the ground line;   a plated layer filled in the plurality of openings and electrically connected to the ground line exposed to bottoms of the plurality of openings;   a ground layer formed of a conductive paste applied so as to continuously cover the second insulating layer and the plated layer, the ground layer covering the signal line and electrically connected to the ground line through the plated layer; and   a third insulating layer covering the ground layer.   
     
     
         12 . The flexible printed wiring board of  claim 11 , wherein the conductive paste has a volume resistivity of 30 μΩ·cm or less.